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Amyloidosis: Abnormal protein deposits in the body

Amyloidosis/Modasta

Amyloidosis is the term that refers to a group of conditions which are rare but serious and caused due to the accumulation of an abnormal protein called amyloid in different tissues and organs of the body. Amyloidosis can affect organs such as liver, spleen, heart, kidneys, digestive tract and nervous system.

Causes

The cause for amyloidosis is a buildup of an abnormal protein called amyloid in the body. Proteins are made up of chains of amino acids that fold themselves into a three-dimensional shape. The folding of the protein is necessary to perform many crucial functions in the cell. When the proteins fold abnormally, they can form amyloid. There are different types of proteins which can misfold giving rise to different types of amyloidosis.

In most cases, amyloid gets deposited in several parts of the body (called systemic amyloidosis) and in some cases in only one location of the body (localised amyloidosis).

The particular type of amyloidosis depends on the kind of amyloid protein deposition:

Immunoglobulin light-chain (AL) amyloidosis or Primary Amyloidosis
This type is the most common form of amyloidosis caused due to the formation of an abnormal protein composed of immunoglobulin light chains in the bone marrow. This type of amyloidosis can affect any organ in the body including heart, kidneys, liver, nerves and skin.

AA amyloidosis or Secondary Amyloidosis

AA amyloidosis is caused by the deposition of a protein called as AA protein. AA amyloidosis is caused by chronic infections or inflammatory conditions such as rheumatoid arthritis, osteomyelitis, inflammatory bowel disease. AA amyloidosis commonly starts in the kidneys but can also affect other organs (such as liver, digestive tract or heart).

Hereditary (familial) amyloidosis

There are many different types of inherited amyloidosis caused by mutations that run in families. One such familial amyloidosis is caused by mutations in a transthyretin (TTR) gene that causes an abnormal transthyretin protein which leads to ATTR amyloidosis affecting the nerves and the heart.
Many other inherited amyloidosis conditions can affect liver, nerves, heart and kidneys.

Dialysis-related amyloidosis

In patients with chronic renal failure who are on dialysis for many years, abnormal proteins called beta-2 microglobulin can accumulate in tissues, especially around joints and tendons causing symptoms such as pain, stiffness and swelling in the joints.

Localized Amyloidosis

Amyloidosis is called localised when abnormal amyloid proteins are formed by local production of immunoglobulin light chains but not formed in the bone marrow. Localised amyloid deposits can form in the respiratory tract, eye, urinary bladder, skin, heart, etc.

Risk factors

Some of the risk factors, associated with amyloidosis include:

  • Age: Majority of the people are diagnosed with amyloidosis after the age of 40 years.
  • Gender: Amyloidosis is more common in men than in women.
  • Family history: Hereditary forms of amyloidosis runs in families.
  • Other diseases: Chronic infections and inflammatory disorders and conditions such as multiple myelomas, increase the risk of amyloidosis.
  • Dialysis: Chronic renal failure patients undergoing dialysis are at greater risk. With the advent of modern dialysis machines, the amyloidosis risk has reduced.

DNA close-up, DNA Molecule Model, DNA Strands, DNA animation

Symptoms

Amyloidosis can present with many symptoms based on the organs affected. Sometimes, people with amyloidosis may not show any symptoms.

Some of the symptoms that are noted in people with amyloidosis include:

  • Kidneys. The ability of the kidneys to filter waste may be reduced. Large amounts of protein may be excreted in the urine causing it to appear foamy. The kidney can gradually stop functioning causing renal failure.
  • Liver. The liver can enlarge significantly and function abnormally.
  • Heart. Irregular heartbeats (arrhythmia) and enlargement of the heart with reduced function (heart failure).
  • Gastrointestinal tract. Thickening of the tongue (macroglossia), malabsorption of food, diarrhoea, clay-coloured stools, difficulty swallowing, reflux of food, constipation and blockages in the digestive tract can happen.
  • Respiratory tract. Breathing difficulties such as shortness of breath can present when there is amyloidosis in the lungs.
  • Nerves. Numbness, tingling, weakness can develop in the arms and legs due to the involvement of nerves (peripheral neuropathy).
  • Joints. Swelling in joints, weak hand grip and other symptoms due to carpal tunnel syndrome.
  • Skin. Thickening or easy bruising and discoloration around the eye.
  • General symptoms. Easy fatigability, unexplained weight loss, anaemia.

Diagnosis

Amyloidosis may go undiagnosed because the symptoms and signs can be very general or resemble other common conditions. Your doctor will take a detailed medical history and examine you. Based on your clinical features, if amyloidosis is suspected, some additional tests may be done to determine the diagnosis.

  • Biopsy. The diagnosis can be confirmed by removing a small sample of tissue from the affected body part and examining under a microscope in the laboratory using special stains to detect amyloid proteins. Samples may be taken from your tummy fat, gut or organs such as liver or kidney.
  • Imaging tests. A particular type of scan called SAP (Serum Amyloid P component ) scintigraphy may be done where a mild radioactive protein is injected, and the person is scanned with a gamma camera. This protein binds with amyloid deposits in the body and is shown in the scan. Other imaging tests such as for liver, spleen and abdominal organs may be done.
  • Laboratory tests. Blood and urine tests may be done to analyse for abnormal proteins.
  • Tests for other organ functions. You may be asked to undergo further tests to see how amyloid deposits have affected your individual organs. For example, echocardiogram for the heart, liver function tests, kidney function tests, and thyroid function tests may be performed.

Treatment

Currently, there is no cure for amyloidosis. The aim of treatment is to prevent further production of abnormal proteins and to monitor the functioning of different organs. This approach can give the body, time to gradually clear the deposits and prevent further organ damage. The specific treatment depends on the type of amyloidosis.

  • AL amyloidosis
    Chemotherapy – to stop the growth of abnormal cells in the bone marrow and inhibit the production of abnormal proteins.
  • AA amyloidosis
    Treating the underlying chronic conditions may help. For example, in rheumatoid arthritis using anti-inflammatory medications to keep the inflammation under check.
  • Hereditary amyloidosis
    The liver is the primary source of amyloid production. Liver transplantation can be very helpful in reducing the amyloid deposits.
  • Dialysis-related amyloidosis
    Symptomatic treatment for relief of joint pain and inflammation such as painkiller medications and corticosteroid injections into the joints. Using high-quality dialysis methods may slow down the progression. Renal transplant may be required in advanced cases.

Other treatments

  • Dietary therapy may be recommended to decrease the effect of amyloidosis on specific organs. For example, if the kidney is affected, a low sodium diet may be recommended.
  • Supportive treatment for specific organs such as dialysis for kidney failure or diuretic treatment for heart failure.
  • Stem cell transplantation – Peripheral blood stem cell transplantation may be useful in some people with amyloidosis who have preserved organ function. Stem cells are collected from your blood and stored before chemotherapy. After chemotherapy, healthy stem cells are returned to your body through a vein, which allows the body to start making healthy blood cells.
  • Surgery: Some people with kidney failure may need a kidney transplant. A heart transplant may be required in those with the severe drop in heart function. Liver transplantation has shown to be effective in certain hereditary amyloidosis.

Complications

The complications of amyloidosis depend on which organs are affected due to amyloid deposits. It can cause failure of liver, kidney, lung, nerve and heart. Also, the treatments given such as chemotherapy, stem-cell and organ transplantation can cause serious side effects.

Next Steps

If you experience any of the symptoms associated with amyloidosis persistently, then visit your doctor.

Red Flags

Once diagnosed with amyloidosis, consider early treatment to prevent progression of disease and organ failures. With modern treatment methods, the prognosis and outlook for amyloidosis have improved considerably.

Consult a top General Physician

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References

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  • NHS choices. Health A-Z. Amyloidosis. Accessed at http://www.nhs.uk/conditions/amyloidosis/Pages/Introduction.aspx on 13 June 2016.
  •  David C. Seldin, Martha Skinner. Chapter 112. Amyloidosis. Harrison’s Principles of Internal Medicine. 18th edition. Copyright McGraw Hill Professional, 2011. •
  • American Society of Clinical Oncology (ASCO). Amyloidosis. Accessed at http://www.cancer.net/cancer-types/amyloidosis/overview on 14 June 2016.

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